Technical note: Use of a double inversion recovery pulse sequence to image selectively grey or white brain matter
ABSTRACT The design of a double inversion recovery (DIR) sequence, to image selectively grey or white brain matter, is described. Suitable choice of inversion times allows either cerebrospinal fluid (CSF) and white matter to be suppressed, to image the cortex alone, or CSF and grey matter to be suppressed, to image the white matter. The DIR sequence was found to give clear delineation of the cerebral cortex.
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- "Prior data were used to estimate the T 1 values for the three brain compartments (GM: 1070 AE 60 ms; WM: 720 AE 30 ms; CSF: 4440 AE 50 ms). With the expression derived by Redpath and Smith (1994), two pairs of T inv1 and T inv2 timings were computed that gave simultaneous nulls of the CSF compartment with either that from GM or WM. Twenty-one 1D projections were acquired for each set of inversion timings. "
ABSTRACT: The pathophysiological underpinnings of bipolar disorder are not fully understood. However, they may be due in part to changes in the phosphatidylinositol second messenger system (PI-cycle) generally, or changes in myo-inositol concentrations more specifically. Dextro-amphetamine has been used as a model for mania in several human studies as it causes similar subjective and physiological symptoms. We wanted to determine if dextro-amphetamine altered myo-inositol concentrations in vivo as it would clearly define a mechanism linking putative changes in the PI-cycle to the subjective psychological changes seen with dextro-amphetamine administration. Fifteen healthy human volunteers received a baseline scan, followed by second scan 75 min after receiving a 25 mg oral dose of dextro-amphetamine. Stimulated echo proton magnetic resonance spectroscopy (MRS) scans were preformed at 3.0 Tesla (T) in the dorsal medial prefrontal cortex (DMPFC). Metabolite data were adjusted for tissue composition and analyzed using LCModel. Twelve adult male rats were treated acutely with a 5-mg/kg intraperitoneal dose of dextro-amphetamine. After 1 h rats were decapitated and the brains were rapidly removed and frozen until dissection. Rat brains were dissected into frontal, temporal, and occipital cortical areas, as well as hippocampus. Tissue was analyzed using a Varian 18.8 T spectrometer. Metabolites were identified and quantified using Chenomx Profiler software. The main finding in the present study was that myo-inositol concentrations in the DMPFC of human volunteers and in the four rat brain regions were not altered by acute dextro-amphetamine. While it remains possible that the PI-cycle may be involved in the pathophysiology of bipolar disorder, it is not likely that the subjective and physiological of dextro-amphetamine are mediated, directly or indirectly, via alternations in myo-inositol concentrations.Neuroscience Research 09/2008; 61(4):351-9. DOI:10.1016/j.neures.2008.04.001 · 2.15 Impact Factor
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- "One sequence used non selective saturation at 4.3s and inversion at 1.65 ms prior to imaging to acquire an image with cerebrospinal fluid (CSF) signal nulled. A second sequence with saturation at 4.3s and inversions at 2408 and 511 ms was designed to simultaneously null CSF and white matter and provide an approximate gray matter image(Bedell and Narayana, 1998; Redpath and Smith, 1994). "
ABSTRACT: Many of the regions with the earliest atrophy in Alzheimer's Disease (AD) do not show prominent deficits on functional imaging studies of flow or metabolism. This paradox may provide unique insights into the pathophysiology of AD. We sought to examine the relationship between function and atrophy in AD using MRI blood flow and anatomic imaging. 22 subjects diagnosed with AD, mean Mini Mental State Exam (MMSE) score 22.2, and 16 healthy elderly controls were imaged with a volumetric arterial spin labeling blood flow MRI technique and an anatomical imaging method using the identical spatial resolution, image orientation, and spatial encoding strategy. Cerebral blood flow (CBF) and gray matter (GM) maps derived from the imaging were transformed to a standard anatomical space. GM and CBF maps were tested for significant differences between groups. Additionally, images were tested for regions with significant mismatch of the CBF and GM differences between groups. CBF was significantly lower in the bilateral precuneus, parietal association cortex and the left inferior temporal lobe but was non-significantly increased in the hippocampus and other medial temporal structures. After correction for GM loss, CBF was significantly elevated in the hippocampus and other medial temporal structures. The hippocampus and other regions affected early in AD are characterized by elevated atrophy-corrected perfusion per cm(3) of tissue. This suggests compensatory or pathological elevation of neural activity, inflammation, or elevated production of vasodilators.NeuroImage 07/2008; 42(4):1267-74. DOI:10.1016/j.neuroimage.2008.06.006 · 6.36 Impact Factor
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ABSTRACT: The objective of the study was to examine the utility of double inversion recovery (DIR) magnetic resonance imaging (MRI) using a 3-T magnetic resonance imager in the preoperative evaluation of hippocampal sclerosis (HS) in patients with mesial temporal lobe epilepsy. This retrospective study had institutional review board approval, and informed consent was obtained. Twelve patients with unilateral HS and 12 age-matched healthy control subjects were included. Imaging was performed using DIR, fluid-attenuated inversion recovery (FLAIR), and T2-weighted turbo spin-echo (T2 TSE) sequences vertical to the hippocampal axis. Quantitative assessment for hippocampus of the patients and control subjects was determined. Regions of interest (ROIs) were placed on bilateral hippocampi, and signal intensity was measured. The signal-to-noise ratio (SNR) of ipsilateral hippocampus, contrast ratio of ipsilateral-to-contralateral side, contrast-to-noise ratio (CNR), and asymmetry index of bilateral hippocampi were calculated and compared among the 3 sequences. Statistical analyses were performed with 1-way analysis of variance and Student t test. On DIR images, HS demonstrated extremely high signal intensity. The hippocampi ipsilateral to the seizure focus showed significantly increased signal intensity, as compared with contralateral hippocampi and healthy subjects (F = 47.876, P < 0.001). The higher SNR of ipsilateral hippocampus on DIR was significant compared with the FLAIR and T2 TSE (P < 0.01). The CNR of bilateral hippocampi on DIR was also significantly higher than that on the FLAIR and T2 TSE (P < 0.01). However, compared with the FLAIR, no significant differences of contrast ratio and asymmetry index between bilateral hippocampi were observed on DIR. Double inversion recovery brain imaging reveals characteristically extremely high signal intensity of hippocampus in patients with HS. Double inversion recovery images can describe HS with high SNR and CNR superior to conventional magnetic resonance sequences and can be valuable for the diagnosis of HS.Journal of computer assisted tomography 35(2):290-3. DOI:10.1097/RCT.0b013e3182073c56 · 1.60 Impact Factor